Arctic winter sea ice shrinks to record low

POLAR bears take note. There was less Arctic sea ice this winter than in any year since records began, bringing the scary prospect of an ice-free Arctic a step closer.

Summer ice has hit a series of record lows in recent years as the Arctic has warmed by almost 2 °C, twice as fast as the mid-latitudes. The ice builds up again each winter and the average extent of winter ice has been declining less steeply, although it has been getting thinner.

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However, this year’s winter refreeze was the weakest since satellite observations began in 1979, according to provisional data from the National Snow and Ice Data Center at the University of Colorado in Boulder. Its peak of 14.5 million square kilometres, reached on 25 February, was around 1 per cent lower than the previous worst, recorded in 2011.

NSIDC researchers are wary of blaming global warming, pointing out that there is a lot of natural variability in ice cover. The unusual path of the jet stream – a high-altitude wind that affects weather – this winter warmed the Pacific side of the Arctic, reducing Bering Sea ice in particular. The ice build-up was also cut short this year because the spring melt began two weeks earlier than usual.

However, Jason Box of the Geological Survey of Denmark and Greenland in Copenhagen says the Arctic is changing profoundly. “We are already in uncharted territory,” he says. “Models are all understating the Arctic response to climate change.”

This article appeared in print under the headline “Arctic winter ice cover plunges to record low”